Vehicle heaters, which are also called "parking heaters" or "auxiliary heaters" in a passenger car, are also used in trucks, buses, campers, boats, but also construction equipment, besides passenger cars.
These vehicle heaters are operated with gasoline or diesel fuel, with a burner heating a heat carrier (air or water).
There are various types of vehicle heaters, which are distinguished, besides according to the type of the heat carrier, according to the type of the fuel (gasoline/diesel fuel) and according to the type of the burner as well as other design features. Besides burners with mechanical atomizers and rotary distributors, there are especially burners with evaporators. These vaporizing burners are of special interest for the present invention.
Vaporizing burners are used not only in vehicle heaters, but also in regenerators for particle filters, which are increasingly used in diesel engines. The cleaning or regeneration of the particle filter is performed by burning out.
The burner being disclosed here may be used equally for vehicle heaters and such particle filter regenerators.
Vaporizing burners contain, besides the combustion air blower, which is also usually used in other types of burners, and the fuel feed pump, which is also usually used, a fuel-evaporating means, typically in the form of a porous lining in the interior of the combustion chamber. Fuel is pumped by the fuel feed pump into this porous lining, so that the liquid fuel is evaporated by the porous material of the evaporator, which material has a large surface. By feeding in combustion air by means of the combustion air blower, a fuel-air mixture is formed, which is then ignited by means of a glow plug. The glow plug, which is typically designed of late as a sheathed element glow plug and is connected to a power source, is switched on to initiate the combustion. The glow plug is switched off after the ignition.
It has been known that the fuel-air mixture must be "ignitable" to form a flame of a fuel-air mixture. Besides the minimal ignition temperature, which is provided by the glow plug and is, of course, always needed, a certain ratio of air to fuel must be present in order for the ignition to be able to take place.
It was now found that the starting of the burner, especially the ignition of the fuel-air mixture, does not always take place with the desired reliability in the vaporizing burner in question.
It is common practice to start the fuel feed pump and the combustion air blower and to switch on the glow plug to start the burner. The blower and the feed pump are operated such that a maximum air and fuel throughput is reached. The environment of the glow plug is increasingly heated during the start-up phase, and when the ignition temperature is reached, the flame is formed, provided that the fuel-air mixture is indeed ignitable. However, it is not always possible to readily satisfy this condition within a relatively short period of time after the burner has been switched on.